Key Takeaways & Executive Findings
- •• Rapid cold punching induces rapid dissolution of precipitates, altering the precipitation behavior during subsequent aging. • Aging temperature critically influences the precipitation sequence: higher temperatures follow the conventional path, while lower temperatures suppress GPB zone formation. • MD simulations reveal that differences in solute atom diffusion rates at different aging temperatures account for the observed variations in S' phase precipitation. • The study provides insights into tailoring aging treatments for Al−Cu−Mg alloys to achieve desired precipitate microstructures and properties.
Abstract
The evolution of the S' precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF−STEM), molecular dynamics (MD) simulations, and other analytical techniques. The precipitation behavior during different aging stages of the supersaturated solid solution formed after rapid cold punching was focused, which induces rapid dissolution of precipitates. The findings reveal that the precipitation sequence is significantly influenced by aging temperature. At higher aging temperatures, which mitigate lattice distortion in the matrix, the precipitation sequence follows the conventional path. Conversely, at lower aging temperatures, where lattice distortion persists, the sequence deviates, suppressing the formation of Guinier−Preston−Bagaryatsky (GPB) zones. MD simulations confirm that the variations in solute atom diffusion rates at different aging temperatures lead to the differences in the S' phase precipitation sequence.
1. Introduction
Al−Cu−Mg alloys are widely utilized in industries such as aerospace, weaponry, and rail transportation due to their high specific strength, excellent heat resistance, and superior formability [1−4]. The strengthening mechanisms primarily include deformation strengthening and precipitation strengthening. Thermomechanical treatment, which integrates both approaches, not only enhances work hardening but also alleviates deformation-induced stress [5−7]. This process facilitates the dispersion, nucleation, and growth of precipitate phases, potentially altering their characteristics and precipitation sequence [8−10].
WANG et al [11] conducted stress-relaxation aging experiments and finite element simulations to investigate the stress-relaxation behavior of aluminum alloys. Their experimental results demonstrated that pre-deformation not only enhances the strength of the samples but also accelerates the aging precipitation process, thereby reducing the time required to reach peak strength. Cold rolling led to variations in the aspect ratios of S phase (Al2CuMg) precipitates during both growth and coarsening stages. IRMER et al [12] studied the effect of cold rolling on the precipitation behavior of Al−Cu−Mg alloys and found that clusters were disrupted during cold rolling and did not reconstitute during natural aging. Solute atoms appeared to be trapped in vacancy-solute clusters by forest dislocations, making them unavailable for the formation of clusters or Guinier−Preston−Bagaryatsky (GPB) zones. HUANG et al [13] employed three-dimensional atom probe, differential thermal analysis, and transmission electron microscopy (TEM) to examine the redissolution of precipitated phase in Al−Cu alloys during plastic deformation and the subsequent reprecipitation behavior during aging. Their findings revealed a significantly accelerated precipitation rate of the θ phase (Al2Cu) following redissolution during the aging process. Moreover, the precipitation sequence deviated from the conventional order, bypassing the transition phases, θ'' and θ', and directly transitioning from the Guinier−Preston (GP) zones to the equilibrium phase θ.
LI et al [14] concluded that the type of precipitates in re-aged samples after cold rolling was influenced by the re-aging temperatures and durations. The precipitated phases mainly consisted of GPB zones at lower temperatures or shorter time, whereas the S' phase was formed at higher temperatures.
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Ze-yi HU, Pu-yu LI, Cai-he FAN, Shuai WU, Yi-ling LU, Yin-chun XIAO, Ling OU (2025). Precipitation behavior of S' phase in rapid cold punched Al−Cu−Mg alloy. SinoTechIntel Verified Research. https://doi.org/10.1016/S1003-6326(25)66949-4
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Frequently Asked Questions
What is the effect of rapid cold punching on the precipitation behavior of Al-Cu-Mg alloy?
Rapid cold punching induces rapid dissolution of precipitates, altering the subsequent precipitation behavior during aging. This process affects the precipitation sequence and the formation of phases like S'.
How does aging temperature influence the precipitation sequence in Al-Cu-Mg alloy?
At higher aging temperatures, lattice distortion is mitigated, and the precipitation sequence follows the conventional path. At lower temperatures, lattice distortion persists, suppressing the formation of GPB zones and leading to a different sequence.
What role do molecular dynamics simulations play in this study?
MD simulations were used to confirm that variations in solute atom diffusion rates at different aging temperatures lead to differences in the S' phase precipitation sequence, providing atomic-level insights.
What are the key findings regarding the S' phase evolution?
The study reveals that the precipitation sequence is significantly influenced by aging temperature, with higher temperatures following the conventional path and lower temperatures suppressing GPB zones, affecting the formation of S' phase.
What techniques were used to investigate the precipitation behavior?
The investigation employed transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), molecular dynamics (MD) simulations, and other analytical techniques.
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